Understanding and addressing the impact of invasive non-native species in the UK Overseas Territories in the South Atlantic

Overview

Results

The team

Related information

So what's the problem?

There is a considerable ongoing threat from invasive alien plant and invertebrate species on all South Atlantic UK Overseas Territories (UKOT). Management plans and capacity building efforts to combat invasive plants are in the process of being developed by various conservation bodies and other research institutions. However there are no current plans to include biological control in these new schemes, despite a long history of successful use on islands in the past. We understand that many species including rare, endangered and/or iconic species are in danger from introduced invasive plants or invertebrates and that the reduction of their impact through biological control would bring tangible benefits to biodiversity in these fragile habitats. At the moment there is very little known about the potential of this tool in South Atlantic UKOTs and this study tries to address this by assessing the feasibility of the future potential usage of this method.

What is this project doing?

The project plans to assess the potential for the integrated biological control of introduced invasive plants on all the South Atlantic UKOTs using a recently-developed prioritisation tool and to make a preliminary review of the potential for biological control of arthropod species prioritised by the ‘South Atlantic Invasive Species Project’ using the arthropod biocontrol database literature held by CABI.

The Falkland Islands and South Georgia will become case studies for in depth assessments of invasive weeds and arthropods seen as priorities and feasible for integrated biological control. This will include updated knowledge about the ecology of such species and their potential control agents, economic comparisons with other currently implemented control methods. The project will assess the islanders' perception of the scale of the problem caused by invasives and their willingness to support biocontrol as a tool for management. In addition, the project will analyse the feasibility for biological control of priority species, such as for the European earwig on the Falkland islands and Cardamine flexuosa on South Georgia.

A major component of this study will be a desk-based review assessing the impact of non-native plants and invertebrates in the South Atlantic UKOTs. We will identify and rank the impacts individual invasive species have had to form a list of priority candidate species for possible future control projects. Priority species will be selected on the basis of population dynamics, reported impact on biodiversity, impact on livelihoods, costs for ongoing control measures other than biological control and others. The feasibility study will include the assessment of current research conducted globally into the target species and will also compile existing information on native range, areas of introduction and recorded natural enemies. Wherever possible, information on host specifity of reported natural enemies will be incorporated. Detailed case studies will evaluate the potential of implementing a biological control programme targetted at each individual priority species for the Falklands and South Georgia. This will include an estimate of costs for whole biological control programmes but also for initial scoping studies. CABI will evaluate both current and potential control methods for priority plant species taking into account the geographical area invaded, associated flora and fauna and a cost-benefit-analysis of the potential biological methods. This will include a catalogue of recommended strategies for each priority target species ranked in order of priority to halt the biodiversity loss through invasive plant and invertebrate species most effectively.

Results so far

Individual non–native species were assessed using the method developed by Paynter et al. (2009), which was modified for the South Atlantic UKOTs and further adapted to assess invertebrate species. These assessments were based on literature reviews, publicly available reports and additional information provided by stakeholders. Preliminary results were refined through stakeholder workshops and field site visits on the Falkland Islands and Ascension, which also allowed stakeholder attitudes to classical biological control to be assessed in more detail.

A major objective of the project was to identify the highest priority species for which biocontrol is likely to provide a cost effective and sustainable management option. The case studies for the Falklands, South Georgia and Ascension Island indicate that a number of high priority species are particularly suitable, and recommended for further more detailed assessments.

For St. Helena and Tristan da Cunha, a preliminary evaluation of priorities for both non-native plants and terrestrial invertebrates was made without the benefit of field visits to sites and detailed stakeholder consultations. Consequently, species for which biocontrol is feasible and recommended are subject to further consideration. Nonetheless, the uptake of biocontrol measures is provisionally highly recommended for the fast spreading Asparagus densiflorus on St. Helena and the scale insect Pseudococcus viburni currently threatening the endemic gumwood trees on St. Helena.

Results from the project, which are currently collated in a final report will be circulated to a wider audience and made publicly available soon.

More details can be found on the project website (www.cabi.org/control_south_atlantic_invasive_species), which will be regularly updated throughout the duration of the project.

Project reports

Calafate spreading at Port Sussex, East Falkland
Dense mat of Mouse-eared Hawkweed spreading at Port Stephens, East Falkland
Dense stands of Mexican Thorn on Ascension
Good biological control of Opuntia by Cactoblastis on Ascension
Gorse spreading near Darwin, Falkland Islands
Mexican poppy, a species encroaching on nesting sites of marine turtles on Ascension
Preliminary results Ascension
Preliminary results Falklands & South Georgia
Project Reference List
Sap-sucking psyllids causing partial control of Mexican Thorn on Ascension
Wild tobacco posing a threat to nesting sites of turtles on Ascension